The Difference Between Preventive and Predictive Maintenance: What Facility Managers Need to Know

For many, the terms “preventive” maintenance and “predictive” maintenance mean virtually the same thing. However, that is far from accurate and knowing the difference can save Facility Managers a considerable amount of time, frustration, and money.

Here’s an example of preventive maintenance:

You’ve recently purchased an economy car. The operator’s manual indicates that the oil should be changed every 3,000 miles. You have the car for three months and that 3,000-mile marker has been reached. So, you dutifully take the car into a fast-change location and have the oil changed. . . whether it actually needs to be changed or not.

Now, here’s an example of predictive maintenance:

Instead of an economy car, the high-end car you now own has what some manufacturers refer to as “condition-based service indicators.” You have had the car three months and now have 3,000 miles on it. Instead of the manual indicating it is time to change the oil, the condition service indicators report that there is no need to change the oil. However, after driving the car 5,000 miles, these indicators say you have 500 miles left before the oil should be changed.

With the economy car, you took the manufacturer’s word for it and changed the oil. However, it is possible you could have gone another 2,000 miles before driving it to the oil-change store. The high-end car self-reported that there was no need to change the oil at 3,000 miles, which likely saved the owner of this car a good $50 or more. Further, it is very likely these savings will continue.

Let’s see how this could apply to Facility Managers.

Your building’s HVAC service provider indicates that the air filters in the building should be checked every month and replaced every three months. In this scenario, we find it costs the Facility Manager $300 each time the HVAC filters are checked and $700 every third month when they are changed. This is an example of preventive maintenance. Once again, we are dutifully following instructions, performing maintenance in anticipation of a need.

However, what if the system was equipped with sensors that could tell us when the filters need to be changed? Having such a system installed could eliminate the $300 monthly inspection, and the system may even indicate the filters do not need to be replaced every three months. Maybe every fourth months is adequate. Now we are saving as much as $900 every quarter because the inspections have been eliminated and we only need to replace the filters three times per year, saving another $700.

The bottom line is this:

Preventive maintenance is typically based on time or usage.

Predictive maintenance, on the other hand, is based on the actual condition of the equipment, not the calendar.

As to the potential for cost savings, a test was conducted using a 29-floor office building in Australia. On average, the building costs $95,000 to $190,000 a year for routine maintenance. Added to this, another $50,000 to $120,000 is incurred for building repairs.

According to Facility Manager, Knight Frank, by taking a predictive approach just involving the facility’s HVAC system, they were able to save $16,742 in operating costs and another $32,300 in repair costs annually. 1

Possibly it is time for facility managers to change their approach, putting more emphasis on predictive maintenance and moving away from preventive maintenance where possible.